GI Secretions II-Covasa

Question 1

Nutrition is impaired if production of pancreatic enzymes falls below ______ of normal levels

Answer 1

10%

Question 2

What secretory products do pancreatic acinar cells secrete?

Answer 2

• trypsinogen
• chymorypsinogen
• protelastase
• procarbocypeptidase A and B
• Anylase
• Lipase
• Nonspecific Esterase
• Prophospholipase
• Deoxyribonuclease
• Ribonuclease
• Procolipase
• Trypsin inhibitors
• Monitor peptide

-Bicarb, Na+, K+ and water are also emitted by epithelial cells lining the ducts==> neutralize stomach acid so digestive enzymes can work effectively

Question 3

What stimulates the secretion of pancreatic juice and bile?

Answer 3

• Secretin:

- occurs in response to duodenal pH allows bile to enter

Question 4

What is the most important stimulant of Acinar cells? What about Ductal cells?

Answer 4

Acinar cells (enzymatic secretion) are stimulated by CCK

Ductal cells (HCO3-) are stimulated by secretin (in response to H+)

Question 5

What enzyme causes the pancreatic ductal cells to release bicarb and water into the small intestine?

Answer 5

Secretin (released in response to acid in the duodenum)

Question 6

What is the most important phase of pancreatic secretion?

Answer 6

Intestinal phase*

initiated by nutrients to cause 65% of pancreatic juice

Question 7

What is the first sign of pancreatic insufficiency? Why?

Answer 7

Steatorrhea (fat in stool)

because pancreatic lipase is the most sensitive to inactivation by low pH –> can’t digest fat

Question 8

How does CF affect the GI tract?

Answer 8

• mutations in CFTR chloride channel cause inability of ducts to secrete HCO3- and water –> enzymes cannot be flushed from the pancreas and limited amounts reach the intestine =malabsorption
• retained pancreatic enzymes can become inappropriately activated and damage the tissue–> pancreatic insufficiency

Question 9

How much of the bile that enters the duodenum is excreted? What happens to the rest of the bile?

Answer 9

• < 10% of bile is excreted
• most of the bile salts (that were deconjugated by bacteria in the GI tract to make bile acids) are returned to the liver through the enterohepatic circulation (portal vein) and taken up by hepatocytes where they are re-conjugated and secreted

(Ileum absorption of conjugated bile acids is active but absorption of deconjugated bile acids is PASSIVE)

Question 10

What regulates bile production and secretion?

Answer 10

• vagal stimulation –> inc in bile production/secretion prior to consuming a meal
• fat and protein in the duodenum –> + CCK release –> inc bile secretion by contraction of the gallbladder and relaxation of the sphincter of Oddi

Question 11

What happens to bile acid biosynthesis during the digestive period?

Answer 11

it is inhibited

-bile acids are synthesized, conjugated and secreted to be stored in the gallbladder during the inter-digestion period

Question 12

What are the different causes of cholestasis? (5)

Answer 12

• Primary biliary cirrhosis (autoimmune destruction of bile ductules)
• Primary sclerosing cholangitis -inflammation and fibrosis of the intra and extra hepatic bile ducts
• Congenital biliary atresia
• obstructive jaundice (gallstones blocking extrahepatic duct)
• cholesterol gallstones (too much cholesterol that is no longer soluble in bile)